1. Field of the Invention
The present invention relates to an imaging apparatus, a radiation imaging apparatus, and a radiation imaging system. For the purpose of the present specification, “radiation” is intended to include electromagnetic waves such as X-rays and γ-rays, as well as α-rays and β-rays.
2. Description of the Related Art
Recently, flat panel type photoelectrical conversion apparatuses and radiation imaging apparatuses have become well known. They are made of amorphous silicon and polysilicon formed as film on an insulating substrate of glass and the like, and structured by two-dimensionally arranging pixels configured by photoelectric conversion elements and TFTs in an area sensor array. These apparatuses normally transfer a signal to a read-out circuit on the basis of charge and read it by performing matrix driving using a TFT on the charge photoelectrically converted by a photoelectric conversion element.
The conventional flat panel type area sensor has a sensor array obtained by two-dimensionally arranging pixels configured by a PIN type photodiode of amorphous silicon and a thin film transistor (TFT) formed on a glass substrate, and is matrix-driven. To the common electrode of the PIN type photodiode of each pixel, a bias voltage is applied commonly through bias wiring over the area sensor from one power source. The gate electrode of the TFT of each pixel is commonly connected to the drive wiring in a row direction, and each drive wiring is connected to a drive circuit configured by a shift register etc.
On the other hand, the source electrode of each TFT is commonly connected to the signal wiring in a column direction, and connected to a read out circuit configured by an operational amplifier, a sample and hold circuit, an analog multiplexer, a buffer amplifier, etc. In the read-out circuit, reference potential is supplied from a common power source to one input terminal of the operational amplifier provided corresponding to each signal wiring.
An analog signal output from the read-out circuit is digitized by an AD converter, processed by an image processing unit configured by memory, processor, etc., and is output to a display device such as a monitor or stored in a record device such as a hard disk.
Relating to a flat panel type photoelectric conversion apparatus using a read-out circuit and a driving circuit for matrix driving of an area sensor array to obtain an image signal or to a radiation apparatus, detailed information is described in U.S. Patent Application Publication No. 2001-012070, Japanese Patent Application Laid-Open No. 2001-340324, and U.S. Pat. No. 6,952,015.
Each of these documents describes, in addition to the basic structure and operation of the area sensor, the configuration of the read out circuit having the amplifier at the initial stage provided corresponding to each common signal wiring. Some documents disclose the configuration of reducing or amending a structural error, that is, an artifact, such as line noise.